It's strange, but easy!

When you're looking at a stack of hardwood lumber and and you begin picking out the boards you like and want to buy, you'll notice that each board has a different width (W), and possibly a different length (L).

Let's say you've found two pieces in the 4/4 stack, one is 8" x 96" and the other is 4" x 96". Should you pay the same price for both pieces? No way! The first board has twice the amount of wood in it (it's twice as wide and the same length)!

The unit of measurement for this kind of lumber, then, is the board foot. It's a measure of the volume of wood that's in a board.

To find the volume of wood, or the number of board feet, simply use this formula. There's a calculator below:

Notice that each measurement - thickness, width and length - are in inches, then divided by 144. You can also come to the same end by measuring just the length in feet, and dividing by 12 instead.

Try This Board Foot Calculator

1. Enter thickness, width, length and quantity.
2. Press Compute to determine board feet.

Notes:

1. Use numbers only, except for slashes ( / )or periods (. )for fractional sizes. Calculator assumes your numbers are in inches, so there's no need to include double quotes ( " ).
2. Hardwood lumber is typically sold by the board foot, a unit of volume equivalent to a board that is one inch thick, one foot wide and one foot long, or 144 cubic inches. Lumber thickness is expressed in quarters of an inch, beginning with 1 inch, so that 1 inch lumber is designated as 4/4, 1-1/2 inch lumber is 6/4, 2 inch lumber is 8/4, and so on. These units refer to nominal or roughsawn dimensions, not surfaced dimensions.
3. This program rounds lumber thickness up to the next 1/4" and lumber less than 4/4 is rounded up to 4/4. Thus, a specified thickness of 3/4" will be treated as 4/4" material.
4. You can enter fractional wood dimensions as decimals (12.75), or as conventional fractions (12 3/4). If you use fractions, just make sure you leave a space between any leading whole number and the fraction.